The palatability advantages of soft, meaty pet foods have long been known, as have the desirable teeth cleaning and storage characteristics of dry, crunchy pet foods. A combination of these two types of pet foods, it logically follows, would be highly advantageous in terms of palatability and teeth cleaning and storage characteristics, and would also provide cosmetic advantages.
Blends of hard and soft textured pet foods have been extensively produced and have achieved notable success. Exemplary of such blended pet foods are those disclosed by Bone et al. in U.S. Pat. No. 4,006,266 and Coffee et al. in U.S. Pat. No. 4,190,679, the disclosures of each of which are incorporated herein by reference. Each of these disclosures relates to the production of a blend of hard and soft textured pet food having both a soft, meaty component and a hard, crunchy component, i.e., two distinct components.
Coextrusion apparatus which can be used to coextrude center-filled foods are also known. Such apparatus generally comprise at least two extruders and a manifold which combines the product of the two extruders and forms the center-filled coextruded pet food. Such coextrusion apparatus are disclosed, for instance, by Schafer in U.S. Pat. No. 3,241,503, which discloses a coextrusion apparatus for forming a concentric pastry; Slaybaugh in U.S. Pat. No. 3,480,445, which discloses a coextrusion apparatus for making a composite puffed cereal product; and Vollink et al. in U.S. Pat. No. 3,499,766, which discloses a coextrusion apparatus for making a puffed multiphased cereal product comprising a soft inner portion enrobed by a dry hard pastry portion.
Hildebolt, in U.S. Pat. No. 3,916,029, teaches the production of a center-filled pet food comprising a proteinaceous inner matrix surrounded by a pastry shell, which is prepared by a coextrusion method. Hildebolt makes mention of the "substantially uniform thickness" of the pastry shell, but only peripherally and without a teaching as to how to achieve such uniform thickness.
The teachings of the prior art relate to the formation of dual textured products "one" at a time, using pilot plant or other low output production equipment. However, when higher outputs are desired for commercial production, multiple dies and orifices are required. The use of multiple orifices leads to differences in flow throughput and production of either slivers or thick products can occur.
None of these prior art teachings provides a means for correcting for such flow variations of either product component which can lead to products having a non-uniform distribution of outer component about inner component.
There remains a present need, therefore, for an apparatus, especially a multi-orifice apparatus, and method for coextruding a center-filled product which is capable of ensuring the substantially uniform distribution of outer component about inner component and products having such substantially uniform distribution.